This invention relates to television systems and, more particularly, to apparatus for selecting frames of video signals indicative of still pictures or motionless images from a succession of frames that includes a portion of frames indicative of moving images.
In the more technologically advanced countries of the world, no one doubts the impact television has as a source of moving picture communication and entertainment that is transmitted over nationwide broadcasting networks. In spite of this, still picture television transmission is growing in the number of present applications. The range of possible uses of still picture television appears to be expanding in such areas as: entertainment (games, puzzles, stories, etc.), management and business functions, advising and counseling, and specific services for handicapped persons. A primary advantage of still picture transmission is that it can be transmitted conveniently by a low transmission capacity media compatible with audio telephone signals and not over the crowded spectrum of the general broadcasting band. In the systems, storage is utilized at the receiver to retain each transmitted frame of video signals and each frame is repeated at the receiver to provide a flicker free picture until the next frame is transmitted.
Heretofore, the effort in still picture broadcasting has been primarily directed toward signal multiplexing, transmission, and other aspects of the system and little attention has been paid to the generation of suitable still picture frames. In face to face type communication via such systems, still pictures or snapshots of the subjects are automatically processed in accordance with the operation of the system. This produces the displeasing subjective effect of transmitting pictures of the subject in ungainly poses, for example, eyes shut, mouth open. Even in situations involving graphical displays, there is a possibility that the transmitted frame may occur as the display is changed and produce a smeared image that is repeated at the receiver. Since the number of different frames used to produce the picture at the receiver is much less in still picture systems than conventional systems, the contribution of each frame to the quality of the program material, whether beneficial or detractive, is far greater for still picture operation than for moving picture operation.
Accordingly, an object of the present invention is to improve the subjective quality of still picture broadcasting by the selection of frames indicative of motionless video images from the succession of frames produced by a video camera.